Interpretive Summary: Unfortunately, the application of amylase (an enzyme) to break down long chains of unwanted starch in U.S. sugarcane factories is still not optimized because of misinformation about which enzyme to use, and how to add the enzyme. Factory trials were conducted to provide more optimum conditions for amylase applications to factory staff. Working solutions of high activity amylase were required to improve contact between the amylase and starch in factory tanks and are more cost-effective than adding amylase undiluted. There is also an important discussion on concern about the use of engineered high temperature stability alpha-amylases, developed for much larger markets than the sugar industry, and possible carry-over activity into raw and refined sugars, molasses, and food products.

Technical Abstract:
In recent years there have been warnings by some U.S. refineries that there may be a penalty for high starch concentrations in raw sugar if starch control is not improved. Most commercial amylases used by the U.S. sugar industry to control starch have intermediate temperature stability (up to 85 degrees C with an optimum ~70 degrees C), and are produced from Bacillus subtilis. Full characterization of commercial amylases are reported in Part I of this study (Eggleston et al, 2007b). Amylase optimization trials in the last evaporator at three factories were conducted across the 2005 Louisiana processing season. Factory 1 typically applied 3.6 ppm/cane wt. of (undiluted) B. subtilis amylase with low activity (59 KNU/ml) for an average starch hydrolysis of 6.6% as determined with an iodometric method, that only increased to 11.4% at a 7.2 ppm dosage; similar disappointing results occurred at Factory 3. At Factory 2, the sameamylase (59 KNU/ml) at 10 ppm (undiluted) gave an average hydrolysis of 25.4% that only increased to 28.5% at 20 ppm. Also at Factory 2, application of a B. subtilis amylase of higher activity (545.3 KNU/ml) at 2 ppm gave an average hydrolysis of 26.7%, but only increased to 29.6% at 5 ppm because of low contact between the enzyme (alpha-amylase) and substrate (starch). Application of the amylase as a working solution diluted 3-fold in water at the factory, improved contact and starch hydrolysis from 31.9 to 42.0% at 2 and 5 ppm, respectively, and is more cost-effective than adding it undiluted.